Use of amylopectin to waterproof dynamite



United States v a ent 3,003,862 USE OF AMYLOPECTIN TO WATERPROOF DYNAMITE Lemuel E. Sentz, Jr., and Matthew A. Curtis, New Castle, Pa., assignors to American Cyanamid Company, New York, N.Y., a corporation of Maine No Drawing. Filed Apr. 7, 1960, Ser. No. 20,546 5 Claims. (Cl. 52-11) This invention relates to explosive compositions and more particularly to improved ammonium nitrate blasting compositions resistant to the action of water and moisture which comprise ammonium nitrate and amylopectin.

Among the various types of blasting explosive compositions in use today, are those comprising ammonium nitrate admixed in various proportions with sodium nitrate, various combustibles and a liquid explosive such as nitroglycerine, drip oil (dinitrotoluenes), and the like. For certain uses, these compositions containing ammonium nitrate are preferred over other blasting compositions. However, during storage and use, these compositions show certain disadvantages in that they deteriorate upon contact with moisture and water. In the handling and use of these compositions, often necessarily under adverse conditions, it is dificult to avoid contact with moisture or water. In contact with water these explosive materials often absorb suflicient water either to show poor strength characteristics or to become progressively inert to detonation. This causes additional hazards and expense in blasting operations, and this disadvantage becomes especially serious when the blasting composition is used in the wet bore holes often encountered in actual field conditions.

In the past, many attempts have been made to improve the water resistance and overcome the disadvantages of ammonium nitrate containing explosive compositions. In one simple solution, the cartridges generally used have been dipped in a parafiin wax or the like, to seal them against water and moisture, but this has been only partly successful. Attempts have also been made to achieve water resistance by admixture of various water-repellent materials with the composition or by coating the particles with water repellent substances or metallic soaps, resins, and the like, but these have likewise been only partly successful. Many commercial ammonium nitrate dynamites have included various varieties of starches for use as a water-proofing material as well as various gums. These too have been only partially successful although they represent some of the best commercial waterproofing agents that the art has known up to now.

We have found that ammonium nitrate dynamite compositions of greatly improved Water resistance can be formulated by the use of from 0.5 to 25% of amylopectin as part of the combustible materials in the composition. Amylopectin is one of the constituents of most starches. It apparently, however, is not present in starches as a free compound in a physical blend, but on the contrary appears to be chemically bonded to the amylose which accompanies it as another constituent of starch. That this is true is evident from the results which we described below in our examples showing that an attempt to reconstitute potato starch by blending 80% amylopectin with 20% amylose (the known relative pro portions) does not reproduce the results obtained with potato starch itself. Also, when waxy maize is used as the starch in an ammonia dynamite the results are much poorer than those obtained with amylopectin, although waxy maize is reported to be composed of as much as 98% amylopectin. Consequently, although starches have been used in the past this does not anticipate the 2 use of amylopectin itself as a water-proofing agent since the latter is a completely difierent chemical species which we have found, very unexpectedly, to have a good ability to Waterproof ammonia dynamite.

Amylopectin for use in the compositions of our invention may be derived from any starch in which it occurs. It must, however, be isolated from the starch as a separate composition. It is a chemical fragment of most starch molecules, no matter what the source, but, unless it is isolated from the starch, the resulting composition is merely the starch waterproofing of ammonia dynamite known to the art and not the amazingly improved waterproofing which is obtained by the used of isolated amylopectin.

In an ammonia dynamite or blasting agent the basic explosive is of course ammonium nitrate, which is preseat as 099.5% of the total composition. The composition may also contain 0-25% nitroglycerine and 0-15 dinitrotoluene as sensitizers. Likewise, other known sensitizers can be used in the usual proportions. Other ingredients which are often added include other nitrates such as sodium or potassium nitrate which is. used to replace some of the ammonium nitrate. Such nitrates may be present to the extent of 048.5% of the total composition (by weight as are all the percentages given herein). There must however be at least as much ammonium nitrate as any of the other nitrates, individually. The compositions having a high amount of ammonium nitrate and other nitrates and little or none of the other ingredients mentioned below (especially no sensitizers) are usually called blasting agents. 7

Ammonia dynamite or blasting agents may also contain at least G25% of a solid fuel for the explosive to oxidize in order to cause the explosion. Such solid fuels are well known in the art and often include such things as bagasse, coal, flour, starch, and the like. The dinitrotoiuene can also act as part of the solid fuel, since it too has a negative oxygen balance (i.e. has insuflicient oxygen to support its own combustion). In the com-= positions of our invention a part of the solid fuel usually is replaced with the amylopectin as described below. There is also used 0-3% of an anti-acid such as, chalk, zinc oxide, or magnesium oxides.

A minimum of about 0.5% of isolated amylopectin is required in the explosive compositions of our inven tion. The amylopectin is often used as a substitute for all or part of the combustibles or solid fuel normally used in the formulation of an ammonium dynamite, since amylopcctin is itself a combustible. Thus, for ex-' ample, in a formulation using uncoated ammonium nitrate in which about 8% corn starches are ordinarily used as a combustible, the substitution of half the starch by amylopectin (that is, 4% amylopectin based on the total composition and 4% starch), results in a dynamite composition with high resistance to the efiects of mois{ ture. Such a composition withstands the effects of mois ture for very long periods of time compared with those compositions using other water-proofing agents. More than 0.5% amylopectin based on the total composition should be used. In fact a minimum of about 4%]is a preferred composition. Much higher compositions are readily usable depending on theeconomics of the situa-' tion.

Also included in our invention is the broader classof non-nitroglycerine explosives in which ammoniumjnitrate is blended only with a petroleum oil, drip oil, or solid fuels. Such a mixture, though not classified asan explosive under the ICC regulations, is made for exam: ple, from seismographic explorations. This too can be protected in our invention by replacement of someoi' all of the solid or liquid fuel with isolated amylopectini Such a non-nitroglycerine explosive needs at least 4% Patented Oct. 10, 1961.

of such fuels, although usually more is employed. The ammonium nitrate can vary in such mixtures from finely divided material as is used in ammonia dynamites to the coarser fertilizer grade material. Again at least 0.5% of .amylopectin can be used.

Fertilizer grade ammonium nitrate is sometimes blended in the field with fuel oil to give a kind of nonnitroglycerin explosive for immediate use on the spot. We include within our invention the protection of such fertilizer grade ammonium nitrate from water by at least 0.5% by weight of the Whole of isolated amylopectin. Thus any size particles of NH NO can be water-prooied with amylopectin in our invention.

In any of these compositions, the amylopectin can be physically admixed with the ammonium nitrate and other ingredients or it can be deposited from solution as a filrnon the ammonium nitrate particles. The latter is preferred for protecting larger particles sizes such as fertilizer grade ammonium nitrate, where as the former is preferred in ammonia dynamite.

The compositions of our invention show greatly improved water-resistance properties. By the use of the methods available in the art for measuring the water resistance of dynamite compositions, it is extremely difficult to obtain reproducible results. Moreover, methods used afiord at best a determination merely of whether or not deterioration caused by water has reached such a state as to result in the composition being completely inertto detonation. By the means known in the art, it is difi'icult if not impossible to obtain quantitative measurements as to the degree of deterioration resulting from contact with water with varying amounts of time, as shown by loss of strength of the explosion. In order to demonstrate this surprising degree of water resistance of our dynamite compositions, a method has been devised by means of which one can reproducibly determine the degree of. deterioration, that is, the relative loss of strength of the explosion resulting from exposure to water with varying periods of time and the limit of water exposure before the composition becomes inert to detonation. Described most simply, the relative strength of the explosion is determined on partially deteriorated samples of the composition by measuring the intensity of the sound of. the explosion. We have found that this gives a. measurement of the relative strength of the explosion which is dependent upon the degree of deterioration by exposure to water. This is further explained in detail in the following paragraphs. An explosive composition is prepared by adding varying amounts of amylopectin to a dynamite formulation in substitution for the combustibles. The usual means of mixing as employed in the art are used.

Thecomposition is then machine packed uniformly into l A" x 8" dynamite cartridges and subjected to the testing method in which the water resistance is determined by the following procedure. The cartridges are completely sealed. with a wax coating (microcrystalline Wax is preferable). The whole cartridge is first dipped in the wax. Then each end is dipped again and finally wax, is ladled into the depressions in the ends. Holes, 2 mm. in diameter, and 17.5 mm. deep, are then punched into the cartridge perpendicular to its longitudinal axis; 16 holes are placed in the cartridge in four staggered longitudinal rows of four punch holes each, each row being at 90 of. arc to the other, the distance between holes in any one row being 1-3.4" and from a given end of the cartridge, the nearest holes for alternate rows beingl" and 1%", respectively.

The punched cartridges are then placed in a water bath, 9" from the surface and firmly supported at the ends and middle in a level and horizontal position being so placed that the holes point in vertical and horizontal directions'in the tank. After being thus exposed to the action of-water for various periods of time, the cartridges are removed and then detonated with a standard No. 6

blasting cap. The intensity of the sound from the explosion of the immersed cartridges is compared with the intensity of the sound from a control non-immersed cartridge of the same formulation. The ratio of the sound intensity from an immersed cartridge to the sound intensity of a non-immersed control cartridge is designated the relative sound intensity (RSI).

The sound intensity of each explosion is determined in a shooting house, 75 feet uphill from the shooting pit, both shooting pit and shooting house being located outdoors in a convenient place such as in a ravine. Practically any sound measuring device may be used. When the readings are in decibels, which are equal to ten times the logarithum of the sound intensity, they are converted to sound intensity for calculation of the relative intensity.

Examples of suitable apparatus are the following:

(1) General Radio Sound Survey Meter, Type 1555- A. Here the maximum needle deflection is measured. Readings are in decibels.

(2) General Electric Sound Survey Meter, Catalog 4980178-G1. Here, also, the maximum needle defiection is measured. Readings are also in decibels.

(3) Brush Electronic equipment, pen-recording type of sound measuring apparatus using a microphone, Brush BA 1%; amplifier, Brush BL 905; recording through a Brush recording oscillograph, Brush BL 202. Here the displacement of the pen as shown on the tracing is proportional to the sound intensity.

The noise of the blasting cap can be ignored, since this is negligible compared with the noise of the exploding dynamite composition. I

The cartridges are immersed for different periods of time and are then detonated. The relative sound intensities as defined above and as obtained by detonating one or more immersed cartridges and comparing with one or more dry cartridges, are then plotted against time (the relative intensity for no immersion is l), to give a curve from which may be read the degree of failure from immersion in water at any particular time up to the time of being inert to detonation. The extent of deterioration for any given time may be determined from the curve. Any particular point may be designated the failure point. As time progresses, even though an explosion takes place, the decreased relative sound in tensity indicates loss of strength of the explosion.

Evidence of stub, i.e., incomplete detonation, is noted by observation; thus, even when only part of the charge detonates there may still be a measurable sound intensity. For convenience for comparison purposes, the time when /3 deterioration has taken place, as determined from the curve, is used as the basis of comparison. This is an extremely useful test for showing the degree of permanence of water resistance which is achieved, it being possible to follow the actual rate of deterioration.

The results of this test showing the rate of deterioration cannot be directly compared with the results in previously published tests since the other tests carried out simply indicate the point in hours after exposure to water as which the cartridge fails to detonate completely. Also these cartridges have been completely waxed to hermetically seal them except for punched openings, while cartridges in previous tests have not always been so treated. There may be considerable deterioration of the composition before detonation fails completely. As stated, the evidence of stub has been the only endpoint designated iu previous tests. In the new test described, it is possible to. follow the progress of deterioration with time of exposure to water.

This application is a continuation in part ofour copending application, SerialNo. 763,202, filed September 25, 1958, now abandoned.

Our invention can be further illustrated by the following examples in which parts are by weight unless otherwise specified.

Example 1 The following is the formulation for a typical ammonia dynamite:

Nitroglycerin 11.8 Drip oil (dinitrotoluenes) 2.2 Ammonium nitrat 37.0 Sodium nitra'n 36.4 Wood pulp 2.0 carbonaceous materials 8.0 Coal 1.6 Chalk 1.0

The following carbonaceous materials were used in the previously mentioned formulation with the given results being the time and hours at which the two thirds intensity of sound (or one third deterioration) occured.

The two samples of amylopectin were from two difierent source materials, the first known to be potato starch and the second from an unknown starch.

We claim:

1. A composition consisting essentially of 15-99.5%

ammonium nitrate, 0-485 sodium nitrate, 0-48.5% potassium nitrate, there being at least as much ammonium nitrate as any of the other nitrates, 0-25% nitroglycerine, O15% dinitrotoluene, 03% of antiacid compound selected from the group consisting of chalk, zinc oxide and magnesium oxide, and at least 0.5% of isolated amylopectin.

2. A composition of matter consisting essentially of at least 0.5 isolated amylopectin and up to 99.5% ammonium nitrate.

3. The composition of claim 1 containing at least 4% amylopectin.

4. A composition having the approximate composition by weight of 11.8% nitroglycerin, 2.2% dinitrotoluene, 37% ammonium nitrate, 36.4% sodium nitrate, 2% wood pulp, 8% isolated amylopectin, 1.6% coal and 1% chalk.

5. The product of claim 1 in which the amylopectin is coated on the surface of the ammonium nitrate.

References Cited in the file of this patent UNITED STATES PATENTS Davis Sept. 19, 1944 OTHER REFERENCES 

1. A COMPOSITION CONSISTING ESSENTIALLY OF 15-99.5% AMMONIUM NITRATE, THERE BEING AT LEAST AS MUCH AMMOPOTASSIUM NITRATE, THERE BEING AT LEAST AS MUCH AMMONIUM NITRATE AS ANY OF THE OTHER NITRATES, 0-25% NITROGLYCERINE, 0-15% DINITROTOLUENE, 0-3% OF ANTIACID COMPOUND SELECTED FROM THE GROUP CONSISTING OF CHALK, ZINC OXIDE AND MAGNESIUM OXIDE, AND AT LEAST 0.5% OF ISOLATED AMYLOPECTIN. 